Thromb Haemostasis
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Comparative Study
Evaluation of a new automated panel of assays for the detection of anti-PF4/heparin antibodies in patients suspected of having heparin-induced thrombocytopenia.
Heparin-induced thrombocytopenia (HIT) is a life-threatening complication of heparin treatment; the prognosis depends on early and accurate diagnosis, and prompt start of alternative anticoagulants. Because of high sensitivity, the commercially available immunologic assays are widely used, though not suited to be run on single samples and with a turnaround time of 2-3 hours. We evaluated two new, rapid, automated, semi-quantitative chemiluminescent immunoassays in HIT suspected patients: HemosIL AcuStar HIT-IgG(PF4-H) (specific for IgG anti-PF4/heparin antibodies) and HemosIL AcuStar HIT-Ab(PF4-H) (detecting IgG, IgM and IgA anti-PF4/heparin antibodies) (both from Instrumentation Laboratory). ⋯ The HemosIL AcuStar HIT-IgG(PF4-H) and HIT-Ab(PF4-H) assays showed a very high sensitivity, and therefore they can reliably be used to rule out HIT in suspected patients. The diagnostic specificity was greatly increased by using the HemosIL AcuStar HIT-IgG(PF4-H). Both the assays are reproducible (CVs <6%), rapid (turnaround time 30 minutes), automated, and semi-quantitative, and they can be run for single sample testing.
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In vitro factor XIII supplementation increases clot firmness in Rotation Thromboelastometry (ROTEM).
Factor XIII (F XIII) is an essential parameter for final clot stability. The purpose of this study was to determine the impact of the addition of factor (F)XIII on clot stability as assessed by Rotation Thromboelastometry (ROTEM). In 90 intensive care patients ROTEM measurements were performed after in vitro addition of F XIII 0.32 IU, 0.63 IU, 1.25 IU and compared to diluent controls (DC; aqua injectabile) resulting in approximate F XIII concentrations of 150, 300 and 600%. ⋯ DC) of approximately 7 mm and 6 mm were observed in FIBTEM and EXTEM, respectively. F XIII addition also led to decreased CFT, increased alphaA, and reduced ML in FIBTEM and EXTEM. In vitro supplementation of FXIII to supraphysiologic levels increases maximum clot firmness, accelerates clot formation and increases clot stability in EXTEM and FIBTEM as assayed by ROTEM in perioperative patients with high fibrinogen and low FXIII levels.
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There is some data available on the role of high on-treatment platelet reactivity by ADP whereas, as regards arachidonic acid or other agonists, there is no proof of the best cut-off for identifying populations with a different cardiovascular outcome by the construction of appropriate receiver-operator characteristics (ROC) curves. We enrolled 1,108 acute coronary syndrome patients undergoing percutaneous coronary intervention (PCI) with stent implantation and followed them up for 12 months. Platelet reactivity was assessed by light transmission aggregometry (LTA) using 10 microM ADP, 1 mM arachidonic acid (AA) and 2 microg/ml collagen. ⋯ The contemporary platelet hyperreactivity to more than one agonist was associated with a higher risk of 12-month cardiovascular death and MI, whereas isolated platelet hyperreactivity to only one agonist had not a predictive value [10 microM ADP LTA>or=55% + 1 mM AA LTA>or=15%: odds ratio [OR]=3.6(2.4-6.1), p<0.0001; ADP LTA>or=55% + 1 mM AA LTA>or=15% + 2 microg/ml collagen LTA>or=31%: OR=4.7(2.9-7.7), p<0.0001]. In this prospective study on a large number of acute coronary syndrome patients undergoing stent implantation, we have found that high on-treatment platelet reactivity measured by LTA induced by more than one agonist--AA, ADP, collagen--is an independent risk factor for 12-month cardiovascular death and non-fatal MI. Isolated platelet hyperreactivity to only one agonist has not a predictive value for clinical recurrences.
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Comparative Study
Comparison of methods for monitoring residual platelet reactivity after clopidogrel by point-of-care tests on whole blood in high-risk patients.
Cardiovascular events are more frequent in high-risk coronary artery disease (CAD) patients on dual antiplatelet therapy with a residual platelet reactivity (RPR) than in those showing inhibition of ADP-inducible platelet activation. It is known that post-interventional RPR is a clinically important entity confirming it as a risk factor for thrombo-ischaemic events. Multiple electrode platelet aggregometry (MEA) on whole blood has been recently proposed as a rapid tool to evaluate RPR in high-risk CAD patients on clopidogrel therapy. ⋯ MEA in relation to LTA showed a sensitivity of 80% and a specificity of 91%. MEA might represent a reliable method and valid alternative in comparison with other available platelet function assays. It might help to guide antiplatelet therapy and thus improve clinical outcome of high-risk CAD patients.